undersampling points in vizualization

Greetings,
I have just started using VisAD. I want to visualize
a 'terrain' of data samples, say 100x100 in longitude
and latitude, with various height values.
I modified P4_01.java from the tutorial to do this.
I also added option buttons to allow me to set PolygonAttributes
to POLYGON_FILL, POLYGON_LINE, and POLYGON_POINT, and to
also setPointMode(true) or (false) on the GraphicsModeControl.
When I setPointMode(true), I see all of my data samples.
When I attempt to show a 'terrain' (POLYGON_FILL) or a grid
(POLYGON_LINE) there is an undersampling of my data points
leading to an incorrect display.
I see the same effect with the original P4_01.java code
when I add my components to change the PolygonAttributes
and/or the PointMode. The 50x50 samples are reduced to 25x25
in the POLYGON_LINE and POLYGON_POINT mode.
I've been digging into the source code to track down just where
my samples are converted to Java3D objects, and I've also
looked in this list archive for previous question about this.
Ideally, I'd like to have control over whether my data is undersampled
or not. I just haven't stumbled on the obvious way to fix that!
Tom Nelson